Pretty much the higher you can jump, the longer hangtime you have. I am sure if you are flailing all over the place then it will cut your hangtime as your momentum takes a shot. Although I swear some people just stay in the air longer like Jordan and "Clyde the Glide". Scientist also say that it's physically impossible to stay in the air for longer than a second if you are jumping manually. Again, I swear guys like Jordan have been in the air for slightly longer.
Not Jordan, but an example:
http://www.youtube.com/watch?v=yeBrB4sE1s0